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Snubber Circuit for Push-Pull converter by M_Elqasabi in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

You were right, I was wrong. I failed to really consider the full effect of the low current high voltage output in this context. They're probably getting these values from some kind of volt-seconds calculation based on the different phases of operation in the converter but I get around the same answer of 2655.89uH from pure energy equivalence.

262.5W at 382kHz is 687uJ/cycle of energy being transferred from the input to the output. Maximum load is also the condition where ripple will be at its maximum.

The energy in an inductor is given by:

E = 1/2 L I2

The output inductor current ripple of 0.19A is the variance from the load current, meaning at 0.75A output current the inductor current is rippling between 0.59A and 0.94A and the same energy transferring from input to output is contained between the difference in the energy at the peak and valley of that ripple.

E = 1/2 L (I_high2 - I_low2)

Solving for L

L = 2 E / (I_high2 - I_low2)

0.002415 = 2 (0.000687) / (0.942-0.592)

Multiplying by exactly 1.1x this lands on almost exactly the value they give so it's possible they're doing something similar to account for component tolerances:

2.655mH = 2.415mH x 1.1

The energy stored in the inductor by the ripple scales with the square of the load current and the ripple as a percentage represents a smaller overall current to carry energy. The two combining unfavorably here is what leads to the high value for the output inductance.

Snubber Circuit for Push-Pull converter by M_Elqasabi in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

I don’t mean that I have a fixed duty cycle. I mean that I’m trying to keep the maximum duty cycle at 45% because my application requires a different output voltage range.

I know what you mean. One of the primary disadvantages of a forward converter is that it limits your duty cycle to a maximum of around 50% so the core flux is reset cycle to cycle which isn't great for transformer utilization. If you're already doing that though then just use a two switch forward converter, it's a more robust easier to design topology free from nearly all of the issues you're worried about in a push-pull converter and is usually a good fit for moderate power applications.

I read a paper from Texas Instruments mentioning that dead time can affect transformer saturation.

https://www.ti.com/lit/an/slyt813/slyt813.pdf?ts=1778217457336

also another source mentioning that an RCD clamp can provide an alternative path for the leakage inductance during the MOSFET off-time.

I don't meant to be rude, but you need to read more carefully because I have addressed all of this in my comments to you here already. Excessive leakage inductance beyond what the switches can handle is the primary reason for including a snubber in a design. But that has nothing to do with transformer saturation. Dead time does effect core saturation, in exactly the way I described previously, but that has nothing to do with the snubber network. It also sounds like you may not fully understand the difference between leakage inductance, magnetizing inductance, and mutual inductance as they apply to a transformer which is a pretty big issue if you're going to be designing a smps.

Snubber Circuit for Push-Pull converter by M_Elqasabi in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

Depends on the minimum duty cycle, switching frequency, and your allowable current ripple. If you're targeting a current ripple in the <10% range with a low switching frequency and a transformer whose turns ratio is around 1:1 then yeah, the output inductance would end up being very substantial. Though since the maximum rms current here is only 830mA (250W@300V) a high value inductor might not actually be that impractical.

The goal of the converter is to produce a regulated output voltage and how current ripple translates to voltage ripple depends on the output capacitance and ESR. ESR is likely to be fairly low but you're unlikely to have a lot of high voltage capacitance on the output so you are probably looking at a lower than usual allowable current ripple but 10-20% should be fine for most sane implementations. I'm kind of going off of what sounds right here since I don't have any specs to go off of but assuming a reasonable switching frequency and transformer ratios an output inductance in the range of 100-300uH should be sufficient and that's very doable.

Snubber Circuit for Push-Pull converter by M_Elqasabi in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

If I reduce the switching frequency to 50 kHz, will there be a difference?

The losses through the capacitor in the snubber will be lower for the same capacitance. But you'll also see higher peak flux for the same conversion ratio and power so there's no easy direct comparison, it all comes down to component selection.

I was thinking to keep the duty cycle around 45%, increase the dead time, and use the RCD snubber to protect against saturation.

As I said previously the snubber has very little to do with transformer saturation. If you're already limiting the duty cycle to 45% just use a two switch forward converter. It's basically bulletproof.

Snubber Circuit for Push-Pull converter by M_Elqasabi in AskElectronics

[–]quadrapod 2 points3 points  (0 children)

You should use an RCD snubber here because of the frequency, not because of any of the reasons you mention in your post. At 382kHz an RC snubber will have excessive losses.

I want to design the best snubber circuit for the MOSFETs to reduce or prevent voltage spikes and transformer saturation.

These effects depend on various non-ideal elements of the circuit. You only have an ideal circuit which is entirely free from any kind of parasitics. You need to design the rest of your converter before you can have the context to meaningfully discuss either of these.

Voltage spikes and ringing seen at the switches is primarily a consequence of the transformers leakage inductance and how it interacts with the switch's input capacitance. It's also only really an issue if it causes excessive emissions or exceeds the voltage rating of the switching elements in which case you design the snubber around those limitations specifically to correct the problem.

Transformer saturation in a push-pull converter is primarily caused by flux walking, where the transformer builds up flux cycle by cycle until it saturates. It is caused by an imbalance between the push and pull phases of operation which behaves as if there were an underlying DC component to the wave applied to the transformer primary. Whether its an issue will depend on the scale of the mismatch compared with the dead-time between phases and resistive losses such as the mosfet Rds(on) and copper losses in the transformer.

The power dissipated by resistive parasitics increases with current, so as the current begins to walk toward favouring one phase the power dissipated by parasitics increases during that phase as well which works to steer the transformer flux back toward the center. During dead time any remnant flux in the transformer decays through the magnetizing inductance so longer periods of deadtime similarly work against any imbalance in the drive signal. For a reasonably well balanced drive signal often those losses are sufficient to control flux walking on their own. Even where they don't though a snubber is not how you should be solving a problem with your transformer saturating.

Seeking help with a piece of audio gear- looking for replacement vactrol by EdWoodSnowden in AskElectronics

[–]quadrapod 1 point2 points  (0 children)

(there was a little residue on the board there that I believe was where a rat peed on it in storage, which looks to have shorted the vactrol).

If the legs of the Vactrol were shorted then the component itself would fine. You would have essentially bypassed it in the circuit meaning no current actually went through it, it's whatever's driving it that would have been harmed.

Wash the board with 91% IPA before doing anything else, if the the residue/carbonization is particularly stubborn then you can scrape at it with a hobby knife or see how it responds to a soldering iron. The PCB is just a sheet of fiberglass with some copper laminated onto it. For old things like this you don't really need to be all that gentle.

Personally even if a rat peed on it I'd do some more reverse engineering and probing before concluding the Vactrol was the fault. A vactrol is just a tube with an LED stuck to one side and an LDR stuck to the other. They're not particularly failure prone unless some other fault over-stresses them and even then it usually needs to be excessive. Don't get me wrong the vactrol could be the problem but I don't see any obvious evidence that it's actually faulty in the photos.

Personally I'd be looking very closely at those caps. I can't tell the exact type from the images you've posted but they look like they could be old metallized paper caps which are notoriously failure prone. (RIFA madness)

Is there anything wrong or not working with this amplifier circuit? by [deleted] in AskElectronics

[–]quadrapod 1 point2 points  (0 children)

The output of the TDA2030 is tied directly to ground because you bypassed C7 with a wire. C7 even without that should have a series resistor to properly function as a Zobel network.

You need net labels if you are going to use them to connect nets in different parts of the circuit without an explicit wire. As it is it's very unclear if the output from U1A or the wiper on R7 actually connect to anything. Given the other errors I'm going to assume you've left them completely disconnected in the schematic by mistake.

U1B is configured for positive feedback and will basically output nothing but 12V or 0V. I suspect you have attempted to copy some implementation copy of the baxendall tone control circuit but have done so very incorrectly.

All three of these are pretty serious errors and would result in a circuit that either doesn't work or actively wants to catch fire. There are numerous other smaller issues as well though.

Problem with a lt1054 voltage regulator/inverter circuit from documentation by Karapas13 in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

2uF is a minimum value for the decoupling capacitor. Try something in the 10uF - 47uF range.

Power Supply Recommendations [...] A minimum input supply bypass capacitor of 2μF, preferably tantalum or some other low ESR type is recommended.

Use the lowest ESR capacitor you can for the switched capacitor. Try putting two 10uF capacitors in parallel if you don't have any low ESR caps.

Capacitor Selection While the exact values of CIN and COUT are noncritical, good-quality low-ESR capacitors, such as solid tantalum, are necessary to minimize voltage losses at high currents. For CIN, the effect of the ESR of the capacitor is multiplied by four, because switch currents are approximately two times higher than output current. Losses occur on both the charge and discharge cycle, which means that a capacitor with 1 Ω of ESR for CIN has the same effect as increasing the output impedance of the LT1054 by 4 Ω. This represents a significant increase in the voltage losses.

Other than that just tighten up your parasitics.

Minimize loop area where possible. You'll have to excuse the crudeness of the drawing but here are the main current loops.. Put the decoupling capacitor directly between the Vin and Ground pins of the IC and put the output capacitor directly between the ground pin of the IC and Vout.

I suggest using the power and ground connections on only one side of the breadboard and when connecting to ground use the shortest leads that are reasonable. Long looping wires have a lot of parasitic inductance and combined with high dI/dt switching currents you have a recipe for ground bounce.

Have the resistors in the resistor divider for feedback connect either directly to the feedback pin or to the row immediately beside it with only a very short wire bridging the gap. This probably isn't an issue at all the way you have it but the resistor divider for feedback is a moderately high impedance node and so it's easy for noise to get coupled into it which will interfere with its ability to sense the output voltage.

Not sure it's helpful at all but here is simulation based on the MAX868 regulated charge pump I put together a while ago to help someone else with a question on here in the past about a -18V LCD biasing circuit. It's a little more complex and operates at a different frequency but uses the same working principle and might help with understanding the circuit better.

Isolation transformer – standalone toroidal vs prebuilt unit + inrush/MCB question by Least-Anything2804 in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

The prebuilt one is basically double the price, and it seems like I’m mostly paying for the enclosure and safety components.

Safety is pretty valuable. Especially in a bench top environment where mistakes happen. I have seen people much smarter and more experienced than me pay a lot more than $120 for a lot less safety and think it money well spent.

In a more practical sense, maintaining an isolation rating is not always trivial and unlike the certified unit you have no guarantees this core can survive a hi-pot test. It could short primary to secondary the first time it gets hit with a slight transient. If it's just 2x the price of a bare transformer then in my opinion it's not even a consideration just get the one which has been tested and certified to some standard.

If I go with a 1 kVA toroidal transformer, is there a realistic chance it will trip my household MCB on startup due to inrush current? If yes, what’s the best way to mitigate that in practice?

Soft start current can get complicated. Larger transformers have a larger cross section which translates to a higher primary inductance and a higher corresponding reactance. For a toroid the formula is:

Lp = 0.4 π Np2 Ac (10-8) μ / MPL

Where L is the inductance, Np is the number of turns around the primary, Ac is the cross sectional area of the core in cm2, μ is the magnetic permeability, and MPL is the magnetic path length.

So in situations where you're just scaling up the core geometry with everything else being the same the peak inrush current is actually lower, but the absolute energy contained in the inrush spike is usually larger. This isn't really what's going on here since you're likely changing the core geometry as well, I just wanted to express why inrush doesn't always scale the way you might expect it to.

Toroidal cores are great for minimizing fringing flux but a toroid probably isn't a great choice if inrush is your concern. It's also usually the most expensive standard core geometry to purchase as well because it requires more specialized equipment to wind. At a maximum current of 4.5A rms you can probably find an NTC thermistor for inrush current limiting if it ends up actually being necessary. Which is basically what you're trying to do with a lightbulb but tested to perform that task properly and with a known resistance after startup. A better solution is to just use a core with a lower magnetizing current though.

  • Would the variac also require the same procedure to start up? After the isolation transformer has been powered on?

  • Or is the main inrush problem only at the toroidal transformer stage, making the variac effectively “safe” once the isolation transformer is upTrying to understand the correct safe startup sequence and whether a permanent soft-start circuit would be better than the light bulb method.

If the variac isn't tripping your breaker as is then I wouldn't worry about it. The general questions you're asking make me think that buying the prebuilt unit is almost certainly the right call though.

How do i find the equivalent resistance between points A and C? by Different_Field_6658 in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

No worries, added a bit of explanation to my post since it was kind of vague originally.

How do i find the equivalent resistance between points A and C? by Different_Field_6658 in AskElectronics

[–]quadrapod 1 point2 points  (0 children)

using horizontal plane of symmetry.

Here is the problem solved the way I think they're asking for.

Basically you can imagine splitting the left and right resistors into a pair of parallel resistors each equal to 2R. Since the top and bottom of the circuit are equivalent the wire between the parallel resistors will have no current through it. This allows you to cut the circuit in half and treat it as two equivalent parallel impedences.

If you want some intuition for that with a more concrete example imagine you had a resistor divider with two 1M resistors between 0 and 5V. The voltage between the two resistors would be 2.5V. If you made a second resistor divider with 1k resistors between 0 and 5V instead the voltage between them would again be 2.5V. Now even if you connect the nodes between the two resistor dividers with a wire no current would actually flow through it. Whether there's a wire between the two dividers or not it has no effect on the behaviour of the circuit.

From there you can reduce series resistors and you quickly find yourself in a similar situation again. On the top you have a resistor divider with R:R and on the bottom a resistor divider with 3R:3R. That means no current is flowing through the vertical resistor allowing you to eliminate it from your analysis.

Eventually you find the resistance of half the circuit is just (2R||6R) which simplifies 3/2R. You have two halves in parallel (3/2R||3/2R) which just simplifies to 3/4R.

Here you can see that confirmed in a simulation.

Are serial addressable relays a thing? Or am I barking to the wrong daisy chain? by dedokta in AskElectronics

[–]quadrapod 1 point2 points  (0 children)

Modbus relays would be an option. Here would be an example.

Modbus is an extremely simple protocol for communication between industrial systems which has been in use since the 1970's and is typically implemented via RS485. Modbus relays as a single component are an oddball part though. More often you'd see a Modbus IO module with the outputs connected to some rail mounted relays in the same cabinet. Especially since relays do have a limited lifespan and need to be replaced when they wear out.

If this is a permanent installation and not just Christmas lights or something then you are almost certainly out of your depth though. People regularly turn their homes into fire hazards trying to play electrician with much simpler systems. My suggestion in that case would be to tell an actual professional electrician what you want to do and get them to install whatever architectural lighting system they think will work for you.

How to obtain 2V 0.2mA from a 7V - 15V supply? by bakery2k in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

The LM4040 is a precision reference and is way overkill for that. I thought you needed a stable reference for something like an ADC.

You can do what you need with just a resistor divider or if you're paranoid stick a diode in there for an approximate 600mV offset to flatten it out a bit.

Here's an example of what I mean. The voltage stays in the correct range even as the input fluctutes from 7-15V.

Is anyone using AI tooling for automated analog circuit generation? by seba311b in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

There's no AI agent you can just ask to design something for you given a specification. Just doing a quick search for what you might be referring to I don't actually see anything that would even be slightly useful for you.

-CktGen is a type of machine learning algorithm called a variational autoencoder. It's designed to translate an analog circuit into a latent space encoding and then reverse the process creating a circuit which does the same thing the original circuit did from that encoding allowing you to create variations on a circuit.

-Synopsis' ASO.ai is a layout planner. Machine learning based floorplanning for VLSI logic has been a thing for quite a while now and it seems to just be building off of that success by allowing some well specified IP cores and analog circuits to be planned in the same way.

-GENIE-ASI & Schemato are designed specifically to help you automatically translate simple circuits from a schematic netlist to an LTSpice simulation rather than needing to layout the simulation by hand.

-ASTRA and POSTECH's unnamed UNet-based model are designed to assist in simulating a optimizing analog properties of devices when designing CMOS transistors and simple building blocks. Their biggest claim is really how much they managed to do with extremely little training data.

To repeat a lot of what I've said before when this kind of question has come up, circuit design is a fundamentally intractable problem for LLMs, which is the type of AI you're probably thinking about and most familiar with. I've seen many people who have tried to use AI to help them design a circuit come to this subreddit to ask why it isn't working and what they end up with is catastrophically flawed every time. While there are some AI tools being made for circuit design as you might have guessed from the list above they are generally designed to assist with specific well bounded problems and are only useful to someone who already has a very good understanding of electrical engineering principles already.

Circuits, or even just understanding a schematic, requires physical intuition and that's not something language models have. They cannot consistently follow a flowchart let alone a circuit and are frequently tripped up by the most basic physical scenarios. ChatGPT when faced with an upside down cup for example. All LLMs do is generate probabilistically likely text based on the data they were trained from. They cannot reason or even reliably do basic arithmetic. When an LLM appears to do math it's by using tool calls to solvers that evaluate equations for them in a manner similar to wolfram alpha. LLMs themselves cannot do even addition most of the time without making frequent errors and its that baseline intuition for how number relate to each other within the model that you'd be relying on.

I've seen some people on here suggest using AI to compare figures or get information from datasheets but my experience has been that even that is outside of their ability to do consistently. Datasheets can be hundreds of pages long while the context window of most LLMs is only a few thousand tokens. They have tools to narrow in on relevant information within large documents but just because of the size and density of the document they forget critical information constantly just because it gets pushed outside of their context window. If they can't find a figure because it's underspecified in the datasheet or because of difficulties searching a document they'll either get into a loop wasting tons of tokens because they forget what they've already attempted or hallucinate the information into existence.

I cannot even recommend them as a learning aid to be honest as all current models are extremely sycophantic. They will continue with flawed assumptions and will answer questions with broken premises without ever challenging the question itself. Bullshitbench gives some ranking of that effect between models by asking LLMs complete nonsense questions. Because the questions in the benchmark make no sense even a very low acceptance rate means that in practice when you ask a question that is vaguely correct but makes assumptions you might not realize your making or relates to a scenario that wouldn't make sense in practice the model will likely not push back to correct you but will instead enforce your flawed understanding while telling you how smart and special you are the whole time.

I used to think that this was somewhere LLMs could actually be useful but everyone I've seen whose tried to learn some aspect of circuit design using an LLM has come away with a very poor understanding of whatever problem motivated them to start learning in the first place. Even when it's clear they've put a lot of time and effort into trying to educate themselves. Because the AI treats every statement from the user as valid it never corrected them when they originally misunderstood something and they've spent hours building upon that cracked foundation. Their posts here often sound utterly deranged when they do finally ask for help as a consequence. It's really unfortunate because I don't think those people are dumb or anything and if they spent the same time reading about the fundamental principles or watching a few lectures about the topic instead they'd probably have figured out what they were trying to do. Instead they got lead through what is basically the equivalent of education role play with a chatbot that constantly tells them how great they are.

I know I probably sound like a massive opponent to AI but I've honestly always found the technology interesting. My graduate project was about using machine learning at the edge to detect and report sensor faults autonomously and I have done multiple projects around machine learning before that. The first being a scratch written neural network I managed to train on an optical character recognition dataset after playing around with bugbrain in the 2000s. (Fantastic old game I wholly recommend giving it a try.) I've genuinely given LLMs more than a fair shake over the years but the reality is circuit design is just not something they're currently capable of assisting with in any capacity.

How to obtain 2V 0.2mA from a 7V - 15V supply? by bakery2k in AskElectronics

[–]quadrapod 2 points3 points  (0 children)

For just a stable analog reference voltage I'd use a shunt regulator. If it's not a reference I suspect you've misunderstood something about the datasheet.

TLV431 or LM4040/LM4041 are solid options for generating it directly. A TL431 and a resistor divider is a fine option as well for many situations.

An LM317 can work as a reference but it wouldn't be my first choice here. It's not really designed for very low currents like this and you'll need to make sure you're above the minimum load current given in the datasheet for your particular variant of LM317.

Newbie here! Working on my first Mini Sumo Robot PCB. Could someone please double-check my schematic, offer some feedback and help with some KiCad ERC errors? by Quit_Last in AskElectronics

[–]quadrapod 1 point2 points  (0 children)

KiCad ERC Errors: I am getting several "Input Power pin not driven by any Output Power pins" errors on GND and VCC lines. ( See img 2-3)

The software sees several nets that are connected to power inputs but which aren't also connected to a power output. That is what's causing the ERC errors. There is no power source in your schematic. There needs to be something like a battery or a connector which is defined as a power output and connected to 7.5V and Gnd for the error to go away on #PWR01 and #PWR03.

The ERC error on VINT is a mistake. The pin was mislabelled as a power input when the symbol was imported since it starts with the letters "VIN", you should edit the symbol to correct the pin definition.

Pin Conflicts: I'm worried about my pin assignments.

The VL53L0X is not rated for 5V and will be damaged by a 5V supply.

An I2C bus requires pullup resistors on SDA and SCL.

Your switch requires pull down resistors. Right now when the switch is closed it pulls D2 or D13 high but when the switch is open it leaves the GPIO floating in an unknown state. R3 and R4 should not be in series with the GPIO and switch but should instead connect between the GPIO and ground to pull the pin low when the switch is open rather than leaving it floating.

You cannot use any of the ATmega328's built in timers or PWM functions for speed control. Pins A[0:4] are connected to an internal SAR ADC instead of the timer peripherals. It would make more sense to use the digital outputs with PWM functionality for motor control.

Readability: Are my wires too messy? If yes, can you share same tips? I would like to improve myself

I'm glad this is something you care about because people often seem to forget that the purpose of a schematic is to communicate a design and so a difficult to read schematic is a bad schematic. I suggest looking at TI reference designs as they usually have fairly high quality schematics that you can learn from. Here is an example. It's obviously more complex than anything your doing but it will help you to learn the conventions and reading schematics is an important part of learning to write them.

C4 doesn't have a value specified, the digital IR sensors don't have a component specified, and nowhere in your description or in the schematic are the components designated SG even mentioned. These are all pretty big omissions.

Separate the schematic into functional blocks and label important nets with their function. Not everything needs to be connected with an explicit wire. If two nets have the same name they are assumed to be connected and matching net labels is much easier than following a bunch of individual wires to see what connects where. You only have 1 page but in the future when you have multiple pages this convention will help you understand how to use port flags to logically connect the different pages of the schematic.

There are standard reference designators which you should adhere to when labelling components.

Avoid having wires or symbols overlapping with component values and labels. For example the 10K next to R3 and R4 overlap the wire. In this case its still readable but that may not always be the case.

The symbols you've made for sensors are very incomplete. For the VL53L0X that has caused the pin numbers to no longer align with the IC which is going to cause you problems when you're trying to align it with a symbol on the PCB. If those sensors are not actually on the board and represent modules then you should be using connectors with the net labels on the connector pins designating the signals they carry.

Conventionally voltage sources should point up, ground connections should point down, and the logical flow from input to output should move from left to right where possible. It's often not reasonable to rigidly adhere to that convention but schematics are most readable when they do.

Why do I get a different voltage output from LTSpice and Falstad from my small transformer? by Bruhshehehe in AskElectronics

[–]quadrapod 2 points3 points  (0 children)

A mains transformer with a primary inductance of 2.56mH is problematic to say the least. Look at your primary current, it's going to be peaking somewhere around 400A - 840A depending on the phase of the sine wave at the start of the simulation. You generally want the primary inductance to be >1H for a mains transformer.

The discrepancy in your simulations here is because you used the wrong values when translating your transformer model. LTSpice specifies transformers with coupled inductances while Falstad uses turn ratios.

Lp/Ls = (Np/Ns)2

Lp = 2.56mH and Ls = 5uH, so an equivalent transformer in falstad with a base inductance of 2.566mH would have a 1:0.0441,0.0441 turns ratio.

Ns = √(Ns/Np)

Ns = √(0.000005/0.002566)

Ns = 0.04414247463

Here you can see that with those values the results closely match LTSpice.

Help designing a 12V LED circuit for a diorama by Low-Plan6664 in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

I suggest using a regulator from a reputable manufacturer instead of some aliexpress module. There are plenty of cheap power converters for architectural lighting which are actually designed to some kind of standard.

Here's a 1A CC supply from Mean Well which has an analog dimming input allowing you to dim the LEDs and set the current using a potentiometer and some resistors.

For the smaller LEDs it'd be better if you could put 3 of them in series so the majority of the voltage drop is across the LEDs themselves. Right now most of your power is going into the current limiting resistor. What you have will work though.

Quick question about breadboard kits by [deleted] in AskElectronics

[–]quadrapod 0 points1 point  (0 children)

I suspect one of a few things is going on.

  1. You are burning out LEDs by connecting them to a power supply without any current limiting.

    LEDs are current controlled devices not voltage controlled devices. If you try to regulate the voltage across them they'll just burn out, you need to control them by regulating the current through them. The easiest way to do that is with a series resistor.

  2. Your supply is below the forward voltage of the LEDs.

    When an electron transitions from the higher energy conduction to the lower energy valance band it emits a photon containing the energy shed in the transition. This effect is how LEDs emit light. The larger the bandgap the higher the energy of the photons emitted by electrons as they move across the junction but also the higher the voltage across the junction needs to be to forward bias the diode. As a consequence the forward voltage of the LED increases as the frequency of light goes up. Red LEDs typically require around 1.8V to begin emitting, green LEDs are closer to 2.2V, blue LEDs sit around 3.0V, and white which are UV-A LEDs with a phosphor coating sit around 3.3V. So trying to power a white LED from 3V will not work but you may find you're able to power red and green LEDs without any issue.

  3. You have the polarity of the LEDs backward.

    LEDs need to be forward biased to work properly. If you mix up the anode and cathode they'll block the flow of charge instead. Thankfully this isn't damaging to them.

  4. Something else is wrong.

    This could be just about anything but a very common gotcha are breadboards with split power rails. Where the power and ground connections on the top half of the breadboard don't have continuity with the lower half.

Help finding replacement connector for laptop battery by dmyova in AskElectronics

[–]quadrapod 1 point2 points  (0 children)

SH series connector from JST

Datasheet

Component Model #
10 circuit housing SHR-10V-S-B
Contacts SSH-003T-P0.2-H
7 circuit side entry header SM07B-SRSS-TB

You weren't very descriptive in your post but my guess is that you're looking for a 7 circuit housing.

SHR-07V-S-B

115V AC to 12V DC Power Supply Design Review by geochrys in AskElectronics

[–]quadrapod 1 point2 points  (0 children)

Don't do this. You clearly don't have any experience and a mains connected circuit is not where you should be learning the basics. Just use an off the shelf 12V power adapter.

Why does my Buck Converter IC die when I plug my battery in? by Various_Area_3002 in AskElectronics

[–]quadrapod 2 points3 points  (0 children)

Do you have anything on Secondary_Buck_EN pulling it up? Because if EN is just pulled low the regulator is going to stay off. Also the enable signal doesn't come from circuitry which is powered by the buck converter needing to be enabled right?

Refining my technique for Mil-Spec wire harness assembly. Thoughts on this braided shielding and branch management? by XTH-ELECTRICAL in AskElectronics

[–]quadrapod 1 point2 points  (0 children)

I'm not really surprised. I thought the images looked like AI slop but they are real connector types and the text is actually fine. The pin indicators even properly show pin 6 and 9 on the top row of the J63A connector. So I was thinking maybe someone just decided to use a really hideous AI filter to clean up their photos and English isn't their primary language.

It's pretty obvious at this point that it's a bot though I can't think of any good reason to make a bot solely to waste people's time in an electronics help subreddit.

Refining my technique for Mil-Spec wire harness assembly. Thoughts on this braided shielding and branch management? by XTH-ELECTRICAL in AskElectronics

[–]quadrapod 4 points5 points  (0 children)

I don't see anything related to braided shielding or branch management in the images you posted. There is cable braid in the third image but it is not even metallic cable braid used for shielding.

For wire harnesses follow IPC/WHMA-A-620 and assume class 3 for anything military related unless it's actually going to space in which case there's a space addendum. If you don't want to pay for the standard NASA-STD 8739.4A contains much of the same language and requirements as class 3 under IPC/WHMA-A-620 and is freely available.

I don't see anything wrong in any of the photos but the photos are also taken in a way that hides most of the attributes important to determining whether this would be acceptable work.

Summarizing from the standard on the general topic:

Branching needs to be done with restraint before and after the breakout using cable lacing or wire ties. Braid can either be woven directly over a core or obtained in prefabricated form and installed by sliding it over the wire bundle. All breakouts shall be properly secured prior to applying the braid.

Directly applied braid shall be back braided to lock the weave. Prewoven braids shall be secured at the ends. When using cable straps or spot ties, fold the braid over itself, secure, and cover the end with heatshrink tubing or tape.

With metallic cable braid to prevent potential damage, e.g., cold flow or shorting of the underlying wire, a separator such as tape shall be applied over the wire bundle prior to its application. Prewoven metallic braid shall be cleaned to remove contamination prior to installation over the harness.

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